The basic configuration of a thermo-nuclear fusion reactor, as presently conceived is shown in FIG. 1. The fusion reactor, generally shown at reference numeral 1, comprises a fusion reactor chamber 3 containing fusion fuel, usually a mixture of deuterium and tritium (D-T), surrounded by a liquid blanket 5. Energy for driving the nuclear reactor is provided by an electrical energy source 7, for example, a charged condenser bank via a transmission line 9. In order to generate fusion reactions in the deuterium-tritium fuel, the fuel must be brought to the plasma state at very high temperature of the order of a few keV (i.e. 1 to 10 keV) (1 keV=11,600,000° K.).
The energy produced by the fusion reactions is carried out of the plasma 11 in the form of neutrons and alpha particles. Bremsstrahlung produced from the plasma during its burning cycle as well as other losses are also carried out of the plasma 11. The energy is deposited in the liquid blanket and converted to thermal energy which is subsequently converted into electricity and returned to the energy source.
In practice, not all of the energy from the energy source is conveyed to the fusion reactor, as some of the energy is lost as heat from the transmission line and not all of the thermal energy generated in the liquid blanket is converted into electricity, i.e. the conversion is not done with 100% efficiency. To achieve a break-even condition, the energy produced by the fusion reaction must equal the energy lost from the reactor system during one complete energy cycle.
The energy inventory of the fusion reactor illustrated in FIG. 1 is as follows, where “a” is the percentage of energy delivered from the energy source to the reactor and “b” is the percentage of thermal energy from the liquid blanket converted to electricity.                E initial available energy        aE portion of the available energy transferred to the plasma chamber        (1−a)E portion of the available energy dissipated as heat in the transmission line. This heat is transferred to the surrounding environment        aE energy transferred from the plasma chamber to the liquid blanket mainly in the form of bremsstrahlung radiation and heat losses        ER energy produced by the fusion reactions. This energy too is transferred to the liquid blanket        aE+ER thermal energy available from the liquid blanket for conversion to electricity        b(aE+ER) portion of the thermal energy converted to electricity that is returned to the energy source        (1−b) (aE+ER) portion of the thermal energy that is not converted to electricity. This energy is deposited as heat in the surrounding environment.        
For energy breakeven, it is clear that one must have:E=b(aE+ER)  (1)from which
                              E          R                =                                            E              ⁡                              (                                  1                  -                                      a                    ⁢                                                                                  ⁢                    b                                                  )                                      b                    .                                    (        2        )            
Assuming, for example, the typical values of a=b=30 percent, then:ER=3.03 E  (3)
This means that the fusion reactions must be able to generate 303 percent of the initial available energy just to have breakeven in this case of a=b=30 percent. For continuous energy production, this energy has to be produced during each cycle of plasma lifetime.
This is a large amount of fusion energy, and the challenge that the fusion research community has faced for the past 50 years lies with the difficulty of generating this amount of energy in one cycle of plasma burning.